This invention relates generally to door closers and more particularly to power actuated door operators having self aligning piston rods for extended service life and improved reliability.
Power actuated hydraulic door operators may have a screw drive to push a hydraulic piston or a pneumatic or hydraulic pump to drive an air or hydraulic piston for displacing the hydraulic piston of the door closer portion of the door operator. In either case, the hydraulic fluid filled cylinder chamber of the door closer portion and the screw drive, pneumatic drive, or hydraulic drive chamber are separated by a head through which a piston rod projects and reciprocates in order to cause the hydraulic piston of the closer portion to either be driven by the power drive piston during opening or to drive the power drive piston during closing of the door. The head has guide bearings and seals surrounding the reciprocating rod to prevent leakage of fluid or air through the head. Commonly, the rod fits snugly in sockets in the faces of the driving and the driven pistons.
In manufacturing, dimensions, angles, fits, and finishes are specified with practical tolerances which allow for mass production and reasonable pricing. The tolerances are usually specified such that parts made in accordance with them will fit together when assembled and will function as intended. Of course, there is a small probability that the tolerances of the parts chosen for a particular assembly will "stack up" such that fits and alignments will be so bad that the assembly is rejected and either reworked or scrapped. Most of the time, however, the tolerance distribution of parts in the assemblies is within acceptable limits.
over time in service, even if the manufacturing tolerances are virtually perfect, the components of the door operator wear or deform, and slight misalignment between the pistons and the reciprocating rod may occur. As operation continues, this misalignment causes wear of the rod, the guide bearings, and the seals in the head. As a result, leakage of the hydraulic fluid and air begins between the two chambers. This results in degraded performance and, eventually, in complete failure of the door operator.
The foregoing illustrates limitations known to exist in present door operators. Thus, it would clearly be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.